IRGen: Add optnone attribute on function during O0

Amongst other, this will help LTO to correctly handle/honor files
compiled with O0, helping debugging failures.
It also seems in line with how we handle other options, like how
-fnoinline adds the appropriate attribute as well.

Differential Revision: https://reviews.llvm.org/D28404

llvm-svn: 304127

3 files changed, 15 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index 0644d1b2834..63300e25d37 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -760,6 +760,7 @@ emitCombinerOrInitializer(CodeGenModule &CGM, QualType Ty,
       IsCombiner ? ".omp_combiner." : ".omp_initializer.", &CGM.getModule());
   CGM.SetInternalFunctionAttributes(/*D=*/nullptr, Fn, FnInfo);
   Fn->removeFnAttr(llvm::Attribute::NoInline);
+  Fn->removeFnAttr(llvm::Attribute::OptimizeNone);
   Fn->addFnAttr(llvm::Attribute::AlwaysInline);
   CodeGenFunction CGF(CGM);
   // Map "T omp_in;" variable to "*omp_in_parm" value in all expressions.
@@ -3515,6 +3516,7 @@ emitTaskPrivateMappingFunction(CodeGenModule &CGM, SourceLocation Loc,
   CGM.SetInternalFunctionAttributes(/*D=*/nullptr, TaskPrivatesMap,
                                     TaskPrivatesMapFnInfo);
   TaskPrivatesMap->removeFnAttr(llvm::Attribute::NoInline);
+  TaskPrivatesMap->removeFnAttr(llvm::Attribute::OptimizeNone);
   TaskPrivatesMap->addFnAttr(llvm::Attribute::AlwaysInline);
   CodeGenFunction CGF(CGM);
   CGF.disableDebugInfo();
diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
index c4cbaa4d6fe..bbedac962d5 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
@@ -861,6 +861,7 @@ llvm::Value *CGOpenMPRuntimeNVPTX::emitTeamsOutlinedFunction(
       D, ThreadIDVar, InnermostKind, CodeGen);
   llvm::Function *OutlinedFun = cast<llvm::Function>(OutlinedFunVal);
   OutlinedFun->removeFnAttr(llvm::Attribute::NoInline);
+  OutlinedFun->removeFnAttr(llvm::Attribute::OptimizeNone);
   OutlinedFun->addFnAttr(llvm::Attribute::AlwaysInline);
 
   return OutlinedFun;
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index ffbcbfcc291..e4e5fce0227 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -907,7 +907,16 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
     return;
   }
 
-  if (D->hasAttr<OptimizeNoneAttr>()) {
+  // Track whether we need to add the optnone LLVM attribute,
+  // starting with the default for this optimization level.
+  bool ShouldAddOptNone =
+      !CodeGenOpts.DisableO0ImplyOptNone && CodeGenOpts.OptimizationLevel == 0;
+  // We can't add optnone in the following cases, it won't pass the verifier.
+  ShouldAddOptNone &= !D->hasAttr<MinSizeAttr>();
+  ShouldAddOptNone &= !F->hasFnAttribute(llvm::Attribute::AlwaysInline);
+  ShouldAddOptNone &= !D->hasAttr<AlwaysInlineAttr>();
+
+  if (ShouldAddOptNone || D->hasAttr<OptimizeNoneAttr>()) {
     B.addAttribute(llvm::Attribute::OptimizeNone);
 
     // OptimizeNone implies noinline; we should not be inlining such functions.
@@ -961,7 +970,8 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
   // function.
   if (!D->hasAttr<OptimizeNoneAttr>()) {
     if (D->hasAttr<ColdAttr>()) {
-      B.addAttribute(llvm::Attribute::OptimizeForSize);
+      if (!ShouldAddOptNone)
+        B.addAttribute(llvm::Attribute::OptimizeForSize);
       B.addAttribute(llvm::Attribute::Cold);
     }